The present disclosure relates to glass-ceramics and precursor glass articles which may be ion exchangeable and/or ion exchanged glass-ceramics, methods for making the same and articles comprising the same. In particular, the present disclosure relates to white, opaque, glass-ceramics and precursor glasses, which may be ion exchangeable and/or ion exchanged, methods for making the same, and articles comprising the same.
In the past decade, as electronic devices such as notebook computers, personal digital assistants, portable navigation device, media players, mobile phones, and portable inventory devices have converged while at the same time becoming small, light, and functionally more powerful. One factor contributing to the development and availability of such smaller devices is an ability to increase computational density and operating speed by ever decreasing electronic component sizes. However, the trend to smaller, lighter, and functionally more powerful electronic devices presents a continuing challenge regarding design of some components of the portable computing devices.
Components associated with portable computing devices encountering particular design challenges include the enclosure or housing used to house the various internal/electronic components. This design challenge generally arises from two conflicting design goals—the desirability of making the enclosure or housing lighter and thinner, and the desirability of making the enclosure or housing stronger and more rigid. Lighter enclosures or housings, typically thin plastic structures with few fasteners, tend to be more flexible while having a tendency to buckle and bow as opposed to stronger and more rigid enclosure or housings, typically thicker plastic structures with more fasteners having more weight. Unfortunately, the increased weight of the stronger, more rigid plastic structures might lead to user dissatisfaction, while the bowing and buckling of the lighter structures might damage the internal/electronic components of the portable computing devices and almost certainly leading to user dissatisfaction.
Among known classes of materials are glass-ceramics that are used widely in various other applications (e.g., in kitchens as cooktops, cookware, and eating utensils, such as bowls, dinner plates, and the like). Transparent glass-ceramics are used in the production of oven and/or furnace windows, optical elements, mirror substrates, and the like. Glass-ceramics are typically made by crystallizing precursor glasses at specified temperatures for specified periods of time to nucleate and grow crystalline phase(s) in a glass matrix. Exemplary glass-ceramics include those based on the SiO2—Al2O3—Li2O glass system having either β-quartz solid solution (“β-quartz ss” or “β-quartz”) as the predominant crystalline phase or β-spodumene solid solution (“β-spodumene ss” or “β-spodumene”) as the predominant crystalline phase.
Known glass-ceramics are formed using a conventional glass melting process that forms a thick sheet of glass (e.g., 15 mm) through a conventional rolling process. The thick sheet of glass is then crystallized through a long ceramming cycle (e.g., 7 to 10 hours) at a specified temperature in a continuous rolling hearth, to generate a glass-ceramic with appropriate predominant crystalline phase and crystalline phase ratio. After processing to the final component geometry, the glass-ceramic can be strengthened via an ion-exchange process to provide specified mechanical properties.
As stated, in view of the foregoing problems with existing enclosures or housings, there exists a need for materials such as glass-ceramics (which may be ion exchangeable or ion exchanged) that provide improved enclosures or housings for portable computing devices. Also, there exists a need for such materials that exhibit improved mechanical properties such as crack resistance, and exhibit improved whiteness levels and/or opaque colors while addressing, in an aesthetically pleasing manner, the design challenges of creating light, strong, and rigid enclosures or housings. Moreover, there is a need for processes for producing such materials in an efficient manner.